10k Coins missing?

A while back I had switched to playing PC, when I connected my Xbox account to my PC account it said something along the lines of, "Congratulations you've received 10,000 coins!" I spent 4k on 40 apex packs which gave me Heirloom shards. After that I didn't buy and Heirloom because I didn't know exactly what to buy yet. Later on I stopped playing for a while and when I came back I had no Heirloom shards. No trace of the rest of my coins either. 

Considering the coins popped up into my account free I didn't think much of reporting it, I also didn't know how to report it. Now, I understand the rarity of Heirlooms and I found out how to report it. 

Honestly, I'm still not sure how the coins appeared in my account since I don't remember ever buying 10k coins. I hadn't played on my Xbox in a few years, so maybe I spent money on the game and it had just registered, or maybe it was refund from something else. 

I'm probably too late to report this anyway since this happened like 6 months to a year ago, but I thought it would be worth a shot because I haven't gotten another heirloom since.